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Old 01-01-2021, 11:29 AM   #1
jimmy12345678
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Default Valve Rattle At High RPM's Under Load (5k RPM+), Faulty VVL Solenoid

I have an engine rattle that I haven't been able to pin down yet, but I have a theory that I'd like to put forth to the group and see what more experienced Subie owners have experienced.

The rattling noise occurs when going up steep grades at high RPM's under load, like 5,000+. A few months back when the noise occurred it set a CEL, P0028 for the Bank 2 Intake Valve Control Solenoid and a noticable "valve rattle" type noise could be heard. I ran a can of BG Engine Performance Restore through the engine to flush out the oil (leftover can from when I worked at the dealership) and so far the code has not come back, but the rattle can still be heard under the conditions I previously said.

A little more background, when I purchased this vehicle (2008 Subaru Impreza 2.5i) it had a leaking VVL oil pressure sensor on Bank 2, which was misdiagnosed as a bad head gasket and is how I ended up with the car, as the owner didn't want to spend that kind of money. I made sure to keep the oil level up driving the car back home and replaced the sensor ASAP after getting the car, but I have no way of knowing whether it's been ran low on oil before I took possession of it.

So what do you guys think? Could this be caused by a failing VVL solenoid (but not bad enough to cause a CEL) or is it more likely I have engine damage that is making itself known by knocking at high RPM's?

Thanks in advance!
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Old 01-01-2021, 03:34 PM   #2
Elbert Bass
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You may have two conditions - gummed up i-AVLS (VVL) causing the code and spark knock creating the noise.
Generally you will get the P0026/28 from low oil level and/or sludge. First step for the P0028 is engine flush (Seafoam/Subaru Treatment) then fresh oil & filter change. Really bad cases oil & filter - flush - oil & filter.

You say it is valve rattle? Are you sure it is not spark knock (pre-detonation)? The conditions you describe is more indicative of spark knock. Have you tried using a different grade/octane fuel? Tier 1 fuel vendor? Generally if you have valve rattle it is present at all ranges/RPM.
One other thing to check - although this is usually below 2500 RPM - rattle from the i-AVLS rocker arms. I have seen techs not pre-load the spring loaded rocker lever and when the i-AVLS rocker is in low lift the mechanism rattles. Wouldn't hurt to check valve lash either. And then there is the timing belt tensioner - again, those usually rattle at idle/low RPM.
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Old 01-01-2021, 11:58 PM   #3
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Originally Posted by Elbert Bass View Post
You may have two conditions - gummed up i-AVLS (VVL) causing the code and spark knock creating the noise.
Generally you will get the P0026/28 from low oil level and/or sludge. First step for the P0028 is engine flush (Seafoam/Subaru Treatment) then fresh oil & filter change. Really bad cases oil & filter - flush - oil & filter.

You say it is valve rattle? Are you sure it is not spark knock (pre-detonation)? The conditions you describe is more indicative of spark knock. Have you tried using a different grade/octane fuel? Tier 1 fuel vendor? Generally if you have valve rattle it is present at all ranges/RPM.
One other thing to check - although this is usually below 2500 RPM - rattle from the i-AVLS rocker arms. I have seen techs not pre-load the spring loaded rocker lever and when the i-AVLS rocker is in low lift the mechanism rattles. Wouldn't hurt to check valve lash either. And then there is the timing belt tensioner - again, those usually rattle at idle/low RPM.

I will try running some 93 octane fuel once the tank gets to around 1/4 full and recreate the conditions to see if it improves/goes away.

I do not know the full maintenance history of this vehicle as the Carfax only lists spotty oil changes and air filter replacements, so I don't know if the timing belt and water pump has ever been done, but I plan on doing it within the next month or two.

I have also been thinking about doing valve lash when I do the timing belt job, I could not find a maintenance interval for adjusting the valves and I also doubt it's ever been done. And I am a maintenance fanatic and want everything to be "perfect" on my vehicles LOL.

I had no freeze frame data stored with the code, nor have I pulled the VVL solenoid to inspect it for sludge, etc., just have ran the BG EPR flush treatment and checked the level weekly. The reason I assumed it was valve train related was because of past experience hearing "lifter ticks" and other similar noises and they come close to the noise my Subie is making, and also because the P0028 code was set while the noise was very prominent and the conditions were where the noise always seems to occur (steep grade going uphill, 5k+ RPM's). I just "assumed" it was losing oil pressure at high RPM's or something similar to that.

What is the procedure for preloading the rocker level and how do you check the clearance? I will keep this thread updated and see what happens with the car
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Old 01-02-2021, 12:00 PM   #4
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Quote:
Originally Posted by jimmy12345678 View Post
I will try running some 93 octane fuel once the tank gets to around 1/4 full and recreate the conditions to see if it improves/goes away.

I do not know the full maintenance history of this vehicle as the Carfax only lists spotty oil changes and air filter replacements, so I don't know if the timing belt and water pump has ever been done, but I plan on doing it within the next month or two.

I have also been thinking about doing valve lash when I do the timing belt job, I could not find a maintenance interval for adjusting the valves and I also doubt it's ever been done. And I am a maintenance fanatic and want everything to be "perfect" on my vehicles LOL.

I had no freeze frame data stored with the code, nor have I pulled the VVL solenoid to inspect it for sludge, etc., just have ran the BG EPR flush treatment and checked the level weekly. The reason I assumed it was valve train related was because of past experience hearing "lifter ticks" and other similar noises and they come close to the noise my Subie is making, and also because the P0028 code was set while the noise was very prominent and the conditions were where the noise always seems to occur (steep grade going uphill, 5k+ RPM's). I just "assumed" it was losing oil pressure at high RPM's or something similar to that.
What is the procedure for preloading the rocker level and how do you check the clearance? I will keep this thread updated and see what happens with the car
No need to pull the solenoid - if the code goes away after you ran the flush and keep the oil topped up you will be fine. Best place to verify sludge will be when draining the oil pan or a look behind the rocker covers.
The "lifter ticks" you are probably used to are from hydraulic lifters, your Subaru does not have hydraulic lifters, hence the reason for a valve lash adjustment. There is no real service interval for valve lash, although most Subaru instructors recommend around 100,000 miles. Given the fact that EJ engines are prone to head gasket failures a competent tech takes time to adjust valve lash when replacing head gaskets.

OK, you have never been behind the rocker cover of a Subaru - It is not so much a preload as it is a black spring loaded lever next to one intake rocker arm on each cylinder. You release the spring to make it easier to remove the rocker assembly. In the photo: The "preload" is when that square tang is behind that round pin to the left of the tang. There is one of those on 1 intake rocker for each cylinder.
You perform valve adjustment like any other rocker arm valve train - set the cylinder to adjust top dead center (valves fully closed), and use a feeler guage between the valve stem and rocker tappet. The rocker tappet has a lock nut and threaded screw to adjust the clearance.
https://www.subaruoutback.org/attach...-1-png.391473/
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Old 01-12-2021, 04:05 AM   #5
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Thread Update

I filled the car up from 1/4 tank with 93 octane and drove it around for a day or so to make sure the gas is sufficently mixed in before recreating the driving conditions that made the problem occur before.

The higher octane fuel did NOT eliminate the rattling noise that occurs around 5k rpm under heavy load, so I don't feel that is it spark knock, although the car did seem to have less power at those rpm's, as if it was pulling timing to correct for spark knock. Also whenever the noise started it was accompanied by an "oil burning" type smell that even my girlfriend noticed and pointed out, I don't know if that helps at all but I thought I'd include it.

Based on my experience as a mechanic, I'm guessing I need to check valve lash and do a valve adjustment to see if that makes any difference, but I am not experienced with Subies, so what do you guys feel would be prudent to look at now that I've eliminated one of the potential causes? It's definitely some sort of engine noise.

Last edited by jimmy12345678; 01-12-2021 at 05:59 PM.
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Old 01-16-2021, 12:32 PM   #6
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Another update

This might be related, but the car has has an intermittent, occasional misfire at idle ever since I've owned it and I've not been able to determine the cause. It's not enough to set a misfire code, but my experienced mechanic feel knows what a misfire feels like, haven't put a lab scope on it yet to see if I can "catch" a miss on one of the cylinders (2 channel Pico). Seems to happen more when the A/C is on, such as in the summer or when running the defroster.

Don't know if the two issues are related or not. Again not familiar with Subarus, although basic engine concepts remain the same across all makes. Didn't know if anyone had seen this problem before or if there was a common issue that caused this.
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Old 01-16-2021, 01:18 PM   #7
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Originally Posted by jimmy12345678 View Post
Another update

This might be related, but the car has has an intermittent, occasional misfire at idle ever since I've owned it and I've not been able to determine the cause. It's not enough to set a misfire code, but my experienced mechanic feel knows what a misfire feels like, haven't put a lab scope on it yet to see if I can "catch" a miss on one of the cylinders (2 channel Pico). Seems to happen more when the A/C is on, such as in the summer or when running the defroster.

Don't know if the two issues are related or not. Again not familiar with Subarus, although basic engine concepts remain the same across all makes. Didn't know if anyone had seen this problem before or if there was a common issue that caused this.
Interesting additional info about intermittent idle misfire. Two things to consider - 1. is a cam off on timing? 2. The other (more likely than timing issue) a valve guide dropping. Pull the exhaust manifold down and look up the exhaust ports to see if one or more valve guides are sticking out in the port farther than the other - there are two in each port.
I have had many valve guides drop in i-AVLS heads and they have always eventually caused a misfire that can't be attributed to normal misfire causes. That may explain the noise too.
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Old 01-27-2021, 06:09 PM   #8
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Originally Posted by Elbert Bass View Post
Interesting additional info about intermittent idle misfire. Two things to consider - 1. is a cam off on timing? 2. The other (more likely than timing issue) a valve guide dropping. Pull the exhaust manifold down and look up the exhaust ports to see if one or more valve guides are sticking out in the port farther than the other - there are two in each port.
I have had many valve guides drop in i-AVLS heads and they have always eventually caused a misfire that can't be attributed to normal misfire causes. That may explain the noise too.
Thread Update:

Today I removed the exhaust manifold to inspect the exhaust valve guides and I found that none of them had migrated out of the head whatsoever, all of them looked exactly the same and none protruded further than any other, so I feel it's safe to say my valve guides are not the issue. I'd say also that the valves aren't burnt because I'm not getting a dead misfire, nor can I see a burnt valve causing a rattle, but I don't know.

Furthermore, I removed the left side (Bank 2) i-AVLS solenoid (which was its own challenge, had to take a bur bit and grind away some aluminium off the mounting bracket in front of it so that the bolt would clear, now is very easy to remove LOL) to inspect it for sludge and to verify that it moved when 12 volts was applied to it, which it did and no sludge or deposits were found on it, so I don't know where to go at this point, other than checking the valve lash. Or there's also the timing belt tensioner, but as you said that noise should also be present at low RPM's as well.

I wonder if the noise could be piston related, such as piston slap at high RPM's or something of that nature? I'm at a loss right now as to what direction to go from here in my diagnostic process.

Last edited by jimmy12345678; 01-27-2021 at 09:35 PM.
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Old 01-30-2021, 09:13 AM   #9
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Anyone have any ideas on what I should check next in order to figure out this problem? I'm at a loss for words and don't know where to go from here given my inexperience working on Subarus.
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Old 01-30-2021, 12:18 PM   #10
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Sure it' not just a heat shield on the exhaust?
Based on the other things you looked at we are back to spark knock. If it happens under load/acceleration that is most likely spark knock. Primary cause for that is air/fuel going lean. I understand you fixation on valves but if you had a problem in the valve train it would most likely happen at all times.
Do you have the capability to see real time fuel trims? Be curious to see what they are cruising at operating temperature as well as the A/F sensor and O2 sensor under load. also check fuel pressure. Have you tried unplugging the MAF and driving it? Does it still happen?
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Old 01-30-2021, 12:56 PM   #11
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Sure it' not just a heat shield on the exhaust?
Based on the other things you looked at we are back to spark knock. If it happens under load/acceleration that is most likely spark knock. Primary cause for that is air/fuel going lean. I understand you fixation on valves but if you had a problem in the valve train it would most likely happen at all times.
Do you have the capability to see real time fuel trims? Be curious to see what they are cruising at operating temperature as well as the A/F sensor and O2 sensor under load. also check fuel pressure. Have you tried unplugging the MAF and driving it? Does it still happen?
Yes I do have an Autel MS906 scan tool and am capable of getting the live data readings, so I will check short and long term fuel trims, A/F and O2 sensor readings, MAF values, etc. while recreating the problem, as well as i-AVLS Duty Cycle and whether the solenoid is open or closed. Any other data PID's you feel would be handy to monitor?

I found something that COULD explain my issue in another thread on this site, tell me if this makes sense to you or if it's gibberish:

Quote:
Originally Posted by MSR View Post
The issue is the avcs gears, log the AVCS timing below 2k, see they float around off targets, gears seals inside are leaking to the wrong side, solenoids keep chasing targets, need to replace the avcs gears and also solenoids burnout chasing it.
This would also explain my "rattle" at high RPM's like that and should be able to be seen by a scan tool but might not set a MIL. When the "rattling" noise was occurring one of the times and I really got on it going up a steep hill, the MIL came on and set the P0028 code.

I've checked all the heat shields on the vehicle and none are loose or rubbing on anything (been burned by loose heat shields before on customer's vehicles) along with the P0028 code setting during the noise occurring makes me certain is it a legitimate problem.

Have not tried driving with the MAF unplugged, what exactly would it mean if the problem went away with the MAF unplugged?

I WILL get to the bottom of what is causing this issue, I might not be the best diagnostic tech but I'm stubborn enough to not give up when there's a problem LOL
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Old 01-30-2021, 03:06 PM   #12
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Quote:
Originally Posted by jimmy12345678 View Post
Yes I do have an Autel MS906 scan tool and am capable of getting the live data readings, so I will check short and long term fuel trims, A/F and O2 sensor readings, MAF values, etc. while recreating the problem, as well as i-AVLS Duty Cycle and whether the solenoid is open or closed. Any other data PID's you feel would be handy to monitor?

I found something that COULD explain my issue in another thread on this site, tell me if this makes sense to you or if it's gibberish:



This would also explain my "rattle" at high RPM's like that and should be able to be seen by a scan tool but might not set a MIL. When the "rattling" noise was occurring one of the times and I really got on it going up a steep hill, the MIL came on and set the P0028 code.

I've checked all the heat shields on the vehicle and none are loose or rubbing on anything (been burned by loose heat shields before on customer's vehicles) along with the P0028 code setting during the noise occurring makes me certain is it a legitimate problem.

Have not tried driving with the MAF unplugged, what exactly would it mean if the problem went away with the MAF unplugged?

I WILL get to the bottom of what is causing this issue, I might not be the best diagnostic tech but I'm stubborn enough to not give up when there's a problem LOL
That post does not pertain to your engine, only turbo engines and FB engines after 2012. You do not have AVCS (variable valve timing). You have i-AVLS (variable valve lift). Two totally different systems/functions.

Please clarify, you never confirmed after the oil flush/change - do you still get the P0028 or not? I assumed it went away (my bad for not asking).
If you still get P0028 then swap the oil pressure switches on the oil control solenoids from left to right then drive it. Does the P0028 come back or does it change to P0026? Then we can proceed further. One step at a time.

Driving with MAF unplugged puts ECM in limp mode. A preprogrammed fuel mixture/ignition timing based soley on engine speed and throttle position. It is assumed that if the engine runs relatively normal in limp mode the engine is relatively good shape mechanically and the issue is related to engine control sensors and/or wiring for sensors.
Lets sort the P0028 first if that is still happening.
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Old 01-30-2021, 06:41 PM   #13
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That post does not pertain to your engine, only turbo engines and FB engines after 2012. You do not have AVCS (variable valve timing). You have i-AVLS (variable valve lift). Two totally different systems/functions.

Please clarify, you never confirmed after the oil flush/change - do you still get the P0028 or not? I assumed it went away (my bad for not asking).
If you still get P0028 then swap the oil pressure switches on the oil control solenoids from left to right then drive it. Does the P0028 come back or does it change to P0026? Then we can proceed further. One step at a time.

Driving with MAF unplugged puts ECM in limp mode. A preprogrammed fuel mixture/ignition timing based soley on engine speed and throttle position. It is assumed that if the engine runs relatively normal in limp mode the engine is relatively good shape mechanically and the issue is related to engine control sensors and/or wiring for sensors.
Lets sort the P0028 first if that is still happening.

No, I have NOT gotten the P0028 code since doing the oil flush back in November (over 2k miles put on since then), nor have I ever gotten a P0026 code either. The noise was occurring when the MIL came on and shortly after I pulled the code and it was the P0028. The code has not come back but the noise still remains and is easily replicated, and I know that sometimes intermittent problems fail to set any MIL's. I can record the noise as well as all the live data PID's needed to get to the bottom of this.

Last edited by jimmy12345678; 01-31-2021 at 12:00 PM.
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Old 01-31-2021, 01:45 PM   #14
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No, I have NOT gotten the P0028 code since doing the oil flush back in November (over 2k miles put on since then), nor have I ever gotten a P0026 code either. The noise was occurring when the MIL came on and shortly after I pulled the code and it was the P0028. The code has not come back but the noise still remains and is easily replicated, and I know that sometimes intermittent problems fail to set any MIL's. I can record the noise as well as all the live data PID's needed to get to the bottom of this.
That means the code and the noise were not related -directly. Now you need to find the cause of the rattle.
Without hearing the noise IN PERSON (don't waste time with a video) all I can give you is what it could be. Normally anything mechanical will be a persistent thing, not intermittent within a very narrow operating range as you describe.

First thing based on what you tell me is spark knock. Spark knock is always associated with acceleration under load like climbing a hill. This can be the result of carbon buildup in the cylinders or a lean condition. You could try an upper engine carbon cleaning to see if that helps. It is sprayed into the intake while the engine is running. On your model I spray in through the canister purge hose nipple on the driver side of the throttle body. You will be looking for Intake Valve Cleaner or Upper Engine Carbon Treatment in a spray bottle. Try this next.
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Old 01-31-2021, 02:38 PM   #15
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That means the code and the noise were not related -directly. Now you need to find the cause of the rattle.
Without hearing the noise IN PERSON (don't waste time with a video) all I can give you is what it could be. Normally anything mechanical will be a persistent thing, not intermittent within a very narrow operating range as you describe.

First thing based on what you tell me is spark knock. Spark knock is always associated with acceleration under load like climbing a hill. This can be the result of carbon buildup in the cylinders or a lean condition. You could try an upper engine carbon cleaning to see if that helps. It is sprayed into the intake while the engine is running. On your model I spray in through the canister purge hose nipple on the driver side of the throttle body. You will be looking for Intake Valve Cleaner or Upper Engine Carbon Treatment in a spray bottle. Try this next.

Are there any brands you can recommend? I have a 3M fuel injector cleaner 3 piece kit sitting in my garage right now that I can use. I also looked up the factory Subie top engine cleaning tool and solvent, as well as saw several others (seafoam, motor medic, etc.). I've personally used the BG ones as well during my time at the dealer.
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Old 01-31-2021, 03:36 PM   #16
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Are there any brands you can recommend? I have a 3M fuel injector cleaner 3 piece kit sitting in my garage right now that I can use. I also looked up the factory Subie top engine cleaning tool and solvent, as well as saw several others (seafoam, motor medic, etc.). I've personally used the BG ones as well during my time at the dealer.
I've used Suby, BG, MOC.
If you are talking about the system where you plumb into the fuel rail and apply through the injectors I wouldn't go to all that trouble. That is iff you have injector issues.
I would just go with any of the name brand spray cans that you can spray in the intake through a vacuum port. Just spray it in near the throttle body so it gets in all the runners, hence using the purge solenoid port.
When I was at the dealer we used the bottled Suby or MOC stuff in a siphon setup with a valve and let engine vacuum draw it in. I propped the throttle at 1500 RPM and set the valve so it would take about 3- 4 minutes to draw 12 ounces.
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Old 01-31-2021, 03:42 PM   #17
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I've used Suby, BG, MOC.
If you are talking about the system where you plumb into the fuel rail and apply through the injectors I wouldn't go to all that trouble. That is iff you have injector issues.
I would just go with any of the name brand spray cans that you can spray in the intake through a vacuum port. Just spray it in near the throttle body so it gets in all the runners, hence using the purge solenoid port.
When I was at the dealer we used the bottled Suby or MOC stuff in a siphon setup with a valve and let engine vacuum draw it in. I propped the throttle at 1500 RPM and set the valve so it would take about 3- 4 minutes to draw 12 ounces.
No this stuff is in an aerosol can with a long spray nozzle that you're supposed to run between the throttle body and the intake tube and it sprays cleaner much the like BG fuel cleaner does, even had a lock on the lid so you could lock it down and rev the engine while it's spraying. I just utilized the nipple you mentioned and stuck the hose inside of it. Car smoked a good bit while it was running and I kept it around 2k RPM's until the can ran out and now seems to run better under heavy acceleration.

Wasn't able to recreate the conditions that cause the noise today because that road is a good 20 minute drive from where I live and it's quite snowy and slushy today, so I'll have to wait to know 100% for sure if there's been any improvement.
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Old 01-31-2021, 04:24 PM   #18
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No this stuff is in an aerosol can with a long spray nozzle that you're supposed to run between the throttle body and the intake tube and it sprays cleaner much the like BG fuel cleaner does, even had a lock on the lid so you could lock it down and rev the engine while it's spraying. I just utilized the nipple you mentioned and stuck the hose inside of it. Car smoked a good bit while it was running and I kept it around 2k RPM's until the can ran out and now seems to run better under heavy acceleration.

Wasn't able to recreate the conditions that cause the noise today because that road is a good 20 minute drive from where I live and it's quite snowy and slushy today, so I'll have to wait to know 100% for sure if there's been any improvement.
We also had the MOC aerosol - I used to spray it in front of the throttle plate like that so I wouldn't have to scrub the plate.
Smoke equals carbon usually. If it has improved but still rattles a little run another can. You may have had a very bad build-up. Snow and slush? I'll stick with 55 and rain...
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Old 02-06-2021, 06:26 PM   #19
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Update:

Finally had a chance to recreate the conditions previously mentioned, and while the noise seems to have lessened some, it is still there along with what I feel is a lack of power, coupled with a "burning" smell that's noticeable under heavy load after about a minute or so.

I'm starting to question whether the cheap Amazon catalytic converter I installed is clogged or failing and causing both a lack of power and valve flutter at high RPM's that are causing both the noise and lack of power up steep grades. I haven't checked back pressure yet but I do have a gauge to do so if that would be prudent.
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Old 02-06-2021, 08:00 PM   #20
Elbert Bass
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Originally Posted by jimmy12345678 View Post
Update:

Finally had a chance to recreate the conditions previously mentioned, and while the noise seems to have lessened some, it is still there along with what I feel is a lack of power, coupled with a "burning" smell that's noticeable under heavy load after about a minute or so.

I'm starting to question whether the cheap Amazon catalytic converter I installed is clogged or failing and causing both a lack of power and valve flutter at high RPM's that are causing both the noise and lack of power up steep grades. I haven't checked back pressure yet but I do have a gauge to do so if that would be prudent.
Yup, that could be your issue. Cheap cat doesn't have enough strata to handle the extra heat/conversion load and expands choking off. Seen it cause power loss before, but never had one cause spark knock. Do you have a cheap A/F sensor in there too?
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Old 02-07-2021, 04:46 AM   #21
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Originally Posted by Elbert Bass View Post
Yup, that could be your issue. Cheap cat doesn't have enough strata to handle the extra heat/conversion load and expands choking off. Seen it cause power loss before, but never had one cause spark knock. Do you have a cheap A/F sensor in there too?
No, A/F sensor and O2 sensors are OE, most likely the original ones. Converter was done in a "pinch" where the MIL was setting a P0420 code and the catalyst was loose inside the manifold causing a rattle at idle. I "cheaped out" because I needed the car repaired to take it on a road trip and the converter on amazon was 1/3 the price of one at Advance/Autozone. Shows you get what you pay for I guess.

How are the Magnaflow Catalytic Converters? I found #52305 on their website and it's the one for my Subie. Just wondering what others have experienced running them.

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Old 02-09-2021, 10:49 AM   #22
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Thread Update:

My only option on catalytic converters via Autozone and Advance being Dorman, and Dorman products being low quality, cheap garbage in most instances, I decided to go with the Magnaflow catalytic converter #52305. I ordered it this morning and will be installing it as soon as it gets here to see if there's been any improvement.

This experience reminds me more and more of why I go with OE parts whenever possible, oftentimes the aftermarket "equivalents" are junk and either don't last or don't work properly out of the box. The low initial price suckers most in (including me at times) but almost every time I've attempted to "cheap out" on parts it's left me frustrated and caused twice the amount of work and headaches as if I'd just bought quality to begin with.

I feel that this will greatly improve my lack of power and hopefully eliminate the rattle that prompted me to start this thread.

Also, how wise would it be of me to replace the A/F and O2 sensors with OE subie ones? I mean they are 13 years old and have 171k on them already, didn't know if it would be a wise "While I'm in there" kind of thing to do or not, as they aren't hard to access or remove (had the whole exhaust manifold off in 15 minutes, granted I was on a lift).

Last edited by jimmy12345678; 02-09-2021 at 01:52 PM.
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Old 02-09-2021, 08:12 PM   #23
Elbert Bass
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Quote:
Originally Posted by jimmy12345678 View Post
Thread Update:

My only option on catalytic converters via Autozone and Advance being Dorman, and Dorman products being low quality, cheap garbage in most instances, I decided to go with the Magnaflow catalytic converter #52305. I ordered it this morning and will be installing it as soon as it gets here to see if there's been any improvement.

This experience reminds me more and more of why I go with OE parts whenever possible, oftentimes the aftermarket "equivalents" are junk and either don't last or don't work properly out of the box. The low initial price suckers most in (including me at times) but almost every time I've attempted to "cheap out" on parts it's left me frustrated and caused twice the amount of work and headaches as if I'd just bought quality to begin with.

I feel that this will greatly improve my lack of power and hopefully eliminate the rattle that prompted me to start this thread.

Also, how wise would it be of me to replace the A/F and O2 sensors with OE subie ones? I mean they are 13 years old and have 171k on them already, didn't know if it would be a wise "While I'm in there" kind of thing to do or not, as they aren't hard to access or remove (had the whole exhaust manifold off in 15 minutes, granted I was on a lift).
I have never seen an aftermarket catalyst that performed very long or very well in any Subaru, granted most of the ones I have replaced were at the low end of the $$$ spectrum. Yes, I would replace your sensors, especially if they are original. It could very well be your A/F that is causing the catalyst to fail. I just replaced one that was causing a persistent rich condition and making a WRX nearly un-driveable.

Don't buy off brand sensors. I would save money and use the ND replacements that crosses to the OEM numbers - possibly DENSO 2349123 & DENSO 2344445. They are basically the OEM parts at about 40% price at places like rockauto. Double check you OEM numbers with your VIN at https://parts.subaru.com/ then check at rock auto, they cross reference OEM numbers on the Denso sensors.
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Old Yesterday, 08:01 PM   #24
jimmy12345678
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Okay, after it was all said and done, the rattle is still present under the same conditions.

I installed the new magnaflow converter with Denso A/F and O2 sensors, had to helicoil one of the exhaust studs back into the passenger side head because the threads pulled out when I went to tighten them, but other than that the job went fine.

I noticed that the rattle is easily replicable at between 45-55 mph, under heavy acceleration (downshifting), and the rattle starts at approximately 4500 rpm and continues to get louder the higher the RPM's go. The car also seems sort of "sluggish" and underpowered at that RPM and gear (4th I'm assuming?) but readily picks up speed in any other gear and so far I've not heard that rattle at low speeds with high RPM's only at 45-55 or so.

Very strange....
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